The present invention relates to flow meters such as vortex shedding meters or swirl meters, which are responsive to a fluid flow. More particularly, the present invention relates to an insertion vortex meter for use with large diameter pipes.
Generally, flow meters sense the flow of liquids or gases in conduits and produce a signal representative of the flow. One type of flow meter for measuring fluid flow is called a vortex flow meter. The vortex flow meter generally measures the fluid flow by detecting approximately sinusoidal pressure changes created by a moving vortex within the fluid flow.
Generally, the vortex flow meter includes an obstacle known alternatively as a shedding bar, bluff body, or vortex generator. The shedding bar is inserted into the fluid flow causing instability of the flow field. Specifically, the shedding bar splits the flow into two paths around the shedding bar, causing vortices to shed from alternate sides of the object at a frequency linearly proportional to velocity of the flow.
As the bar splits the fluid flow, vortices are created in the fluid flow. These vortices are sometimes referred to as shedding vortices. The shedding vortices produce an alternating differential pressure across the shedding bar at a shedding frequency. This differential pressure is converted into an electrical signal by a piezo-electric sensor. The frequency of the differential pressure or electrical signal is proportional to the velocity of the fluid flow.
In general, vortex meters for larger size fluid conduits tend to be less economical than differential pressure meters or insertion-type meters, in part, because of the large amount of steel or other materials required to produce the standard vortex meter body. In particular, conventional vortex meters are typically sold as a pre-fabricated unit having a pipe section with a flange on each end and a vortex flow meter centered within the pipe section. Such pre-fabricated sections are expensive to produce, because they contain a great deal of metal. Additionally, such sections are expensive to ship because of their weight. Finally, conventional flow meters require that the flow meter be installed between pipes, requiring either that the pipe be cut to insert the flow meter or that the flow meter be installed at the time of the original installation.
There is a need for a vortex-type flow meter that can be produced economically and used with large diameter pipes. There is also a need for a vortex-type flow meter that can be installed into an existing pipe system without having necessarily to stop the fluid flowing within the pipe.